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View Full Version : 4.2 ups and downs?



Metalcorpse
07-03-2015, 01:04 AM
So say I was rebuilding my engine and cash wasn't an issue. What's the pros and cons of the 4.2 kit?

dthompson
07-03-2015, 08:20 AM
assuming you stay with the SC block, and that you use appropriate components, and have the ability to get it tuned appropriately, i don't believe there are any cons other than cost. You might heear some people make the argument that the stock sc 3.8 crank is forged and the 4.2 crank is cast. That is a true statement, however, I do not believe it to be a con. There are many of us running cast 4.2 cranks out there with no problems making good power. As for the pro's... its obviously a bigger displacement because of the increased stroke. In the grand scheme of things... if you are going for a significant increase in power and you are already buying new rods and pistons, it doesn't cost that much more to do the 4.2 than the 3.8.

Metalcorpse
07-03-2015, 07:38 PM
Cool. I am starting my budget for my rebuild. Can the 4.2 make the block less reliable?

dthompson
07-03-2015, 07:47 PM
Budget money for a good tune. That's what makes any of this stuff relaible.

davec73
07-03-2015, 07:54 PM
No real down side to a 4.2 unless you try to cut corners. I would just consult with Dalke on what you need to get it done right the first time. The heads should defiantly be ported well and the cam you run will make a difference as well.

Jacob_Royer
07-04-2015, 08:25 AM
A fully built 3.8 vs a fully built 4.2 is not much cost difference because you have to buy Wiesco pistons and h beam rods for both builds and they BOTH have to be balanced so the only cost difference is the crank shaft it self and you can get one for about 250$ so at that point its a no brainer IMO

XxSlowpokexX
07-07-2015, 11:29 AM
If cost Is not an issue get a custom billet 4.2 crank and never have to worry.. Otherwise Id say just do a 3.8

XR7 Dave
07-07-2015, 11:40 PM
Pro's:

More torque
More HP
Lower boost means lower ACT's which allows more advance and, well see above.
Pump gas friendly, moreso than 3.8L

Con's:

Possibly weaker crankshaft.
Costs a few dollars more.

David Neibert
07-10-2015, 12:10 PM
Pro's:

More torque
More HP
Lower boost means lower ACT's which allows more advance and, well see above.
Pump gas friendly, moreso than 3.8L

Con's:

Possibly weaker crankshaft.
Costs a few dollars more.



I've had the 4.2 you built me since 2009, and at 500 rwhp crankshaft strength is not one of my concerns.

David

Metalcorpse
07-10-2015, 12:29 PM
500? Wow nice. A small concern for me is the idle and if it would still pass smog in ca

David Neibert
07-10-2015, 12:54 PM
500? Wow nice. A small concern for me is the idle and if it would still pass smog in ca

Idle is determined by cam and tuning and it's very possible to get a stock sounding idle from a 4.2, and I'm sure one could be built to pass CA emissions too. Just isn't going to make as much power as it could.

David

820
07-10-2015, 01:12 PM
I think if I were you, I would be talking to some Cali tuners. They should know the smog laws. What part of California are you from? I have a girlfriend who lives a couple blocks from the ocean down around Dana Point. Boy was she fun!!! Loved to be on my bike. She went home when her mom fell ill. We had fun like only a few can know. :)))

Metalcorpse
07-10-2015, 05:09 PM
I'm in Central Valley ca. Near sacramento. If I could cam it I probably would. Just money is the issue

S_Mazza
07-10-2015, 07:04 PM
Idle is determined by cam and tuning and it's very possible to get a stock sounding idle from a 4.2, and I'm sure one could be built to pass CA emissions too. Just isn't going to make as much power as it could.

David

Ideally, it should be 4.2/3.8 = 1.105 = original plus 10% harder to get it to pass emissions. I say this because, at least here in PA, our sniffer limits are based on a certain normal reading per liter, times engine displacement. They won't adjust the standard for your larger engine. (The last thing you would want to do is tell a CA smog inspector that you have internal engine modifications!!!)

The truth is, though, with a good tune and functioning cats, you should be well below the standards. If you are borderline, this could cause an issue.

20psiofevil
07-10-2015, 09:25 PM
The extra displacement is worth it. 260ci with a .030 over bore.

820
07-10-2015, 10:04 PM
I still think you should be talking to local tuners. They know the laws and what it takes to pass. Where there is room to fudge and room not to fudge. If I understand you will be given a set of numbers for a certain year 3.8 supercharged Ford v-6. Only you will have 4.2 liters of displacement. Will the added displacement make it more tough to pass? I would want somebody that is familiar with the local codes. You say money is tight, guess I would want to know that my combination can be made legal so I can enjoy my hard work. Only a California shop can tell you if they even think it will work. My SC is a California car and appears to be stock. It runs very good. Stop light to stop light it will hold it's own. This is a hobby that is expensive and more expensive in certain parts of this great country.

XR7 Dave
07-11-2015, 09:42 PM
Ideally, it should be 4.2/3.8 = 1.105 = original plus 10% harder to get it to pass emissions. I say this because, at least here in PA, our sniffer limits are based on a certain normal reading per liter, times engine displacement. They won't adjust the standard for your larger engine. (The last thing you would want to do is tell a CA smog inspector that you have internal engine modifications!!!)

The truth is, though, with a good tune and functioning cats, you should be well below the standards. If you are borderline, this could cause an issue.

This makes no sense at all. The emissions are based on percentages or PPM counts, not volume. Displacement has nothing to do with it.

Don't look to local tuners to do anything, they can't even pull data from an SC, much less tune it. The best they'll be able to do is read tailpipe emissions for you and check for codes which won't actually help you with planning mods.

S_Mazza
07-12-2015, 02:26 AM
This makes no sense at all. The emissions are based on percentages or PPM counts, not volume. Displacement has nothing to do with it.

You know what, Dave? You're mostly right, so I take back what I said.

In PA at least, the methodology is to take the exhaust gas concentrations (which, as you said, are independent of engine displacement). Then they multiply that concentration by the engine's displacement to come up with the total emissions score. (Even though, as you pointed out, the engine size is really irrelevant to the actual test procedure.)

But that engine displacement used in the calculation would be based on the originally equipped 3.8L size, and I doubt there is a way to change it (even if someone was crazy enough to tell a tester that their engine displacement had increased).

So the score would never increase as I thought it might, because it would always be based on the originally stated 3.8L engine size.

820
07-12-2015, 07:06 AM
Is any one in California passing emmissions with a stroker motor? Without having a daily tune then an emissions tune, or worse having a daily engine or parts and then having an emission engine or parts. If so what type of power level?

XR7 Dave
07-12-2015, 09:45 AM
I haven't built a stroker for anyone in CA, but I would assume there are a couple out there. Without having direct experience I can't answer the question exactly, but I am both an engine builder and one of the very few people in the entire country who can competently tune an SC, so I can probably shed some light on this just the same.

There is no reason why a stroker wouldn't pass CA emissions. A basic formula for decent power and still passing emissions in CA would go as follows:

4.2L with stock compression.
Retain EGR if your car had it.
Mildly ported heads with bigger valves and upgraded valvetrain
Special CA camshaft
Ported 95 blower with 10% MP crank pulley and 5% JS pulley
42lb or larger injectors
Either a stock or a double IC if you feel that it wouldn't be noticed in the visual inspection. IC fan or two.
Ported 70mm stock MAF
70mm TB (yes some of them have carb #'s).
MP raised top.
Ported exhaust manifolds
Exhaust is not that important other than it must retain 3 cats. Just ditch the stock resonator and I recommend dual 2.25" or 2.25" into 3" back to 2.25".
A custom tune.


This combination will make 260-290rwhp and it will pass emissions in any state basically because it won't cause an increase in emissions over stock. Also, there is generally NO reason to have an "emissions tune" unless your car is way out of these parameters and you are trying to get something to pass that really shouldn't.

Metalcorpse
07-12-2015, 01:48 PM
Dave where can I find a Ca legal camshaft? ~~~~ where can I find Ca legal anything? I cant tell if the stuff on SCP has a carb number on it. unless you guys want to be my best friend and sell me some old parts :P